Field of the Invention
The invention relates to an installation for processing wafers in at least one clean room. The installation has a configuration of production units for carrying our individual production steps on the wafers. The production units and measuring units are connected via a transport system for feeding and removing the wafers.
Such installations contain a multiplicity of production units with which different production steps for processing the wafers are carried out. The production steps involve, in particular, etching processes, wet chemical processes, diffusion processes and diverse cleaning processes, such as, for example, chemical mechanical polishing (CMP) processes. For each of the corresponding production steps, one or more production units are provided. In addition, measuring units in which the quality of the processing of the wafers can be inspected are provided. All the production steps that are carried out in the production units are expediently inspected with such measuring units.
The entire production process is subject to strict purity requirements, so that the production units and measuring units are disposed in a clean room or in a system of clean rooms.
The wafers are fed in predetermined batch sizes to the individual production and measuring units via a transport system. To this end, the wafers are transported in transport containers, which are configured in the form of cassettes for example, the transport containers each receiving the same number of wafers. The removal after the processing of the wafers in the production and measuring units is also effected via the transport system, the wafers being stored in the same transport containers in the process.
The transport system has a conveyor system that is configured, for example, in the form of roller conveyors. In addition, the transport system has a storage system having a plurality of storage devices for storing transport containers containing the wafers. The storage devices are expediently configured as stockers. Such stockers are storage systems in which wafers are stored under clean-room conditions.
In known installations for processing wafers, a batch of wafers which is collected in a transport container is directed via the transport system through all the production and measuring units of the installation. In the process, the batch maintains its association with the respective transport container. Therefore, the wafers of different batches are not intermixed.
In this case, for processing the wafers, a respective transport container containing a batch is fed to a production unit via a loading and unloading station. After the processing of the wafers in the production unit, the batch is delivered again to the transport system in the same transport container via the loading and unloading station.
To inspect the production step carried out in the production unit, the transport container is then fed to a corresponding measuring unit, which likewise has a loading and unloading station.
In the measuring unit, it is checked whether the individual wafers of the batch have been correctly processed. In the process, the wafers are normally classified according to defect-free wafers, rejected wafers, which have defects which cannot be removed, and wafers to be reworked, which will meet the required quality again by reworking.
The rejected wafers, which can no longer be used, are separated from the production process, whereas the transport container is filled again with the wafers to be reworked and with the defect-free wafers, and these wafers are delivered via the unloading station. Since some wafers of the batch are sorted out as rejects, gaps remain in the transport container.
A disadvantage in this case is that, in such installations, transport containers only partly filled with wafers are in circulation. This not only results in insufficient utilization of the transport capacities. On the contrary, this also involves a long transit time of the wafers through the installation. In this case, it is especially disadvantageous that, during subsequent production processes in which a plurality of batches are combined, no optimum utilization is achieved. This includes, in particular, oxidation processes that are carried out in furnaces. During the processes, in order to avoid gaps in a transport batch, the gaps are filled with xe2x80x9cdummyxe2x80x9d wafers until the number of wafers corresponds to the original batch size. Such dummy wafers, apart from the wildcard function in the transport batch, the wildcard function ensuring a homogeneous temperature distribution inside the furnace, have no further function and are of no use in particular for the further production process in the installation.
This makes it necessary to temporarily store such transport containers in separate storage systems in order to feed them at a suitable later moment to production units in which the reworking of the wafers to be reworked can be effected. The defect-free wafers likewise disposed in the transport container are carried along in the batch in the transport container at the same time. This results in considerable waiting times for the defect-free wafers.
Published, Non-Prosecuted German Patent Application DE 37 35 449 A1 discloses a production system for wafers that is composed of a plurality of interchangeable transport modules, process modules and inspection modules. Each process module has in each case at least one process station, one storage place and one manipulating device.
The wafers are supplied in a first cassette via the transport module. The manipulating device removes the wafers from the first cassette and feeds them to the process stations and storage places. Useless wafers are detected in the inspection module and are collected, if need be, in a second cassette. The second cassette may serve to temporarily store the useless wafers. Alternatively, the useless wafers are discharged from the inspection module. The defect-free wafers are collected in cassettes and are delivered again to the transport module.
Published, Non-Prosecuted German Patent Application DE 195 14 037 A1 relates to a transport device for conveying substrates. The transport device is configured as a rotary table that is driven at a uniform clock frequency. The substrate can be fed by a rotatably mounted substrate gripper to a process station provided outside the rotary table.
Published, Non-Prosecuted German Patent Application DE 195 23 969 A1 discloses an IC transport system that can be operated in conjunction with a tray-like magazine or a bar-shaped magazine. By a method for the repeated testing of modules in an IC inspection handling apparatus, modules stored in the magazine are repeatedly tested without intervention by an operator and the modules are sorted according to the test results and stored in the magazine.
Published, Japanese Patent Application JP 08268512 A relates to a storage unit for storing substrates. The storage unit contains a sorting unit, by which the substrates are automatically sorted and are put into or taken out of storage in cassettes in the storage unit.
It is accordingly an object of the invention to provide an installation for processing wafers that overcomes the above-mentioned disadvantages of the prior art devices of this general type, in which a material flow of the wafers through the installation is as efficient as possible.
With the foregoing and other objects in view there is provided, in accordance with the invention, an installation for processing wafers in at least one clean room. The installation includes a multiplicity of production units for carrying out individual production steps on the wafers, a measuring station having at least one measuring unit for inspecting the wafers and an unloading station, and a transport system connecting the production units to the measuring station. The transport system feeds and removes the wafers to and from the production units and the measuring units. The unloading station delivering the wafers to the transport system. Transport containers are provided and are transported on the transport system. The transport containers include first transport containers to be filled with defect free wafers from the measuring station, second transport containers to be filled with the wafers to be reworked, and third transport containers to be filled with rejected wafers. The first, second and third transport containers are marked differently. The first, second and third transport containers are loaded from the measuring station separately from one another via the unloading station, and the second transport containers filled with the wafers to be reworked are delivered to the production units for carrying out reworking processes.
According to the invention, the measuring stations are provided in the installation for processing the wafers, the measuring stations each having one or more measuring units and at least one unloading station for delivering the wafers to the transport system.
In the measuring station, first transport containers are filled with defect-free wafers that have successfully passed the inspection in the measuring unit or measuring units of the measuring station. Second transport containers are filled with the remaining wafers, which are not free of defects. In this case, the second transport containers are expediently filled with wafers to be reworked. Finally, third transport containers are filled with rejected wafers, which can no longer be reworked.
Via the unloading station of the measuring station, the different transport containers are delivered to the transport system separately from one another. In this case, the first, second and, if need be, third transport containers are marked differently, preferably in different colors and are delivered via various unloading ports of the unloading station, which are preferably marked in a corresponding manner.
The essential advantage of the installation according to the invention consists in the fact that first transport containers that are completely filled with defect-free wafers are delivered via the measuring station. Only these wafers remain in the production process in the installation, so that an optimum degree of utilization of the transport containers is achieved, which also leads to a considerable reduction in the transit time of the wafers through the installation. The rejected wafers can be discharged completely from the production process at the outlet of the measuring station. The second transport containers filled with wafers to be reworked, if need be after being stored temporarily, are fed to production units for carrying out the reworking processes. It is especially advantageous in this case that the second transport containers no longer contain any defect-free wafers, so that no unnecessary waiting times arise for the defect-free wafers. The reworking processes themselves also become more efficient as a result, since only the second transport containers in which wafers which are only to be reworked are located are fed to the corresponding production units. Corresponding sorting operations are therefore dispensed with. Finally, it is advantageous that the different markings of the first, second and third transport containers makes it possible to assign the different transport containers to the respective production and measuring units without any errors and in a simple manner.
In accordance with an added feature of the invention, the unloading station has separate unloading ports and the first, second and third transport containers can be loaded via the separate unloading ports.
In accordance with an additional feature of the invention, the first, second and third transport containers are marked with different colors. The first transport containers are marked with a green color, the second transport containers are marked with a yellow color, and the third transport containers are marked with a red color. The unloading ports are marked with the different colors of the transport containers assigned to the unloading ports.
In accordance with another feature of the invention, a storage system is provided for temporarily storing at least one of the second transport containers and the third transport containers. The storage system has storage devices and the second and third transport containers are temporarily stored in separate ones of the storage devices.
In accordance with a further feature of the invention, at least one of the wafers to be reworked in the second transport containers and the rejected wafers in the third transport containers are removed from storage manually at the unloading ports of the unloading stations.
In accordance with another added feature of the invention, the wafers have markings for identifying them.
In accordance with a further additional feature of the invention, the wafers supplied in predetermined batch sizes to the measuring station are singularized in the measuring station.
In accordance with a concomitant feature of the invention, the wafers are processed individually in the measuring station, and the at least one measuring unit is one of a plurality of measuring units. Additionally, the measuring station is one of a plurality of measuring stations.
Other features which are considered as characteristic for the invention are set forth in the appended claims.
Although the invention is illustrated and described herein as embodied in an installation for processing wafers, it is nevertheless not intended to be limited to the details shown, since various modifications and structural changes may be made therein without departing from the spirit of the invention and within the scope and range of equivalents of the claims.
The construction and method of operation of the invention, however, together with additional objects and advantages thereof will be best understood from the following description of specific embodiments when read in connection with the accompanying drawings.